From GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband

3.6 Core Network Mobility Management

From the point of view of the MSC and the SGSN, the mobile device can be in any of the MM or PMM states described below. The MSC knows the following MM states:

• MM Detached: The mobile device is switched off and the current location of the subscriber is unknown. Incoming calls for the subscriber cannot be forwarded to the subscriber and are either rejected or forwarded to another destination if the Call Forward Unreachable (CFU) supplementary service is activated.
• MM Idle: The mobile device is powered on and has successfully attached to the MSC (see Attach procedure). The subscriber can at any time start an outgoing call. For incoming calls, the mobile device is paged in its current Location Area.
• MM Connected: The mobile device and MSC have an active signaling and communication connection. Furthermore, the connection is used for a voice or a video call. From the point of view of the RNC, the subscriber is in the Cell-DCH RRC state as this is the only bearer that supports circuit-switched connections.

The SGSN implements the following PMM states:

• PMM Detached: The mobile device is switched off and the location of the subscriber is unknown to the SGSN. Furthermore, the mobile device cannot have an active PDP context, that is, no IP address is currently assigned to the subscriber.
• PMM Connected: The mobile device and the SGSN have an active signaling and communication connection. The PMM connected state is only maintained while the subscriber ...